Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle; the medusa is normally the sexual phase, which produces planula larva that disperses widely and enters a sedentary polyp phase before reaching sexual maturity.

Jellyfish is a carnivorous feeding a variety of planktonic species such as crustaceans, mollusks, copepods, and young worms. Plankton is taken in a layer of mucus covering jellyfish. The body of jellyfish has tiny hair-like structures producing currents by beating. Currents transfers captured plankton towards the edge of the bell where it is discarded with arms and passed to the mouth. Tentacles around the margins of bell or arms bear stinging cells that are used occasionally for catching other prey and small fishes. They have separate sexes and fertilization occurs internally. The sperm is taken into the female body by mouth. Fertilized eggs are subjected to undergo development in pockets in arms that surround the mouth. During autumn the free-swimming larvae are released and after some time, they settle and form into tiny sessile animals that reproduce asexually and release free-swimming miniature immature jellyfish known as ephyrae feeding on plankton and becomes mature after three months. Mainly they are free-swimming marine animals having umbrella-shaped bells and trailing tentacles. Bell can beat for providing propulsion and efficient locomotion. Their lifecycle is complex. Normally medusa is the sexual phase; planula larva could disperse widely and is followed by sedentary polyp phase.

They could be found all over the world to the deep sea from the surface waters. Exclusively, scyphozoans are marine but some are hydrozoans having similar appearances living in freshwater. Jellyfish are large and colorful being common in coastal zones worldwide. Most of the species of medusa get mature within few months, are fast-growing, and die soon after breeding but the polyp stage that is attached to the seabed has a long life. They have roamed seas for somewhat 500 million years and maybe possibly 700 million years or more that makes them the oldest multi-organ animal group.

In certain cultures, jellyfish are consumed by humans as a delicacy in some Asian countries. The species of Rhizostomae are pressed and salted to eliminate excess water.

Body system

Aurelia does not possess respiratory parts such as lungs, gills, and trachea. Being a small organism, it respires by diffusing oxygen from the water through a thin membrane. Within the gastrovascular cavity, high oxygenated water can come in and low oxygenated water can be expelled by ciliated action by promoting the diffusion of oxygen through cells. Aurelia is supposed to diffuse more nutrients and oxygen to cells by a large surface area membrane to volume ratio.

Aurelia has a basic body plan consisting of several parts. The animal has a shortage of excretory, respiratory, and circulatory systems. Adult medusa of Aurelia has transparent look with umbrella margin membrane and tentacles being attached to the bottom. They have 4 bright circular gonads which are under the stomach. The food is passed through muscular manubrium and radial canals help to disperse food. There is the middle layer of gastrovascular, mesoglea cavity having gastrodermis and epidermis. It has a nerve net that is responsible for contraction in swimming muscles and also feeding responses. Adult ones could measure up to the diameter of 40 cm.

Young during the larval stage, planula, contains the small ciliated cell and after freely swimming in the plankton for a day or more, it settles on an applicable substrate where it transforms into a special type of polyp known scyphistoma that divides by strobilation into small ephyrae swimming off for growing as medusae. The increasing size is less than 1 m in the planula stage and up to 1 cm in the ephyra stage and then to several cm in diameter in the medusa stage.

Locomotion

They are considered to be the most energetic and efficient swimmers. They move through water by expanding and contracting radially its bell shaped bodies in order to push water behind them. It pauses between expansion and contraction for creating two vortex rings. They use muscles to contract body that sheds first vortex and pushes animal forward. Mesoglea is elastic which assists the expansion to be powered exclusively by relaxing bell releasing stored energy from contraction. Doing so, 2^nd vortex ring rolls under it and starts to spin faster. It sucks in water that refills the bell and is pushed up against the center of the body providing it secondary or free boost forward. This mechanism is known as passive energy recapture and works at low speeds and also relatively small body sizes that allow the animal to drive 30 percent farther on each swimming cycle. They achieve a 48 percent lower cost of transport in comparison to other animals in similar studies.

Reproduction

Jellyfish contains separate sexes i.e. they are either female or male. For reproduction, males and females release sperm and eggs into the water for sexual reproduction. They develop larvae after fertilization which results in new jellyfish and settle in the sea bottom as polyps. By means of asexual reproduction, this polyp helps to develop new free-living jellyfish.

Feeding

These species feed on plankton which includes organisms such as crustaceans, mollusks, rotifers, tunicate larvae, protozoans, young polychaetes, fish eggs, eggs, diatoms, and other small organisms. They also feed on gelatinous zooplankton such as ctenophores and hydromedusae. Both larvae of Aurelia and adult medusae have nematocysts for capturing prey and in order to protect themselves from predators. Foods are tied with mucus and are passed down by ciliated action down into the gastrovascular cavity where serious cell digestive enzymes break down food. There is limited information about the need for particular minerals and vitamins but because of the presence of some digestive enzymes, we could deduce in general that Aurelia aurita can process proteins, carbohydrates, and lipids.

Predators

Aurelia aurita is are the prey of Ocean Sunfish (Mola mola), the scyphomedusa Phacellophora camtschatica, the Leatherback Sea Turtle (Dermochelys coriacea), and very large hydromedusa (Aequorea victoria). Sea birds fed upon moon jellies.

History

Jellies are regarded as one of the oldest animals on Earth, with a history dating back between 500 and 700 million years. They are the first known animal to have a nervous system which makes it an important step in evolution of life.

Types of Jellyfish

Within the phylum of Cnidarians, it is possible for differentiating four large groups, each with its own characteristics. They are as follows:

• The class Hydrozoa – They alternately show the phases of polyp and jellyfish. Generally, they are small in size and could be solitary or colonial. This class includes siphonophores. It is floating colonies of polyp individuals or jellyfish having abundant poisonous cells which are used for self-defense and in some cases, it could be harmful for people. Siphonophores form complex colonies of individuals who are specialized in various functions. Some serve as flotation organs and others for defense, nutrition, and feeling. Portuguese men of war (Physalia physalis) or By-the-wind sailor (Velella spirans) are the best-known species that could cause painful burns for bathers and even heart failure.
• The class of Scyphozoa – This group is known as true jellyfish. Normally, they are great marine jellyfish having very short and even non-existent polyp phases. Species such as mauve stinger or purple jellyfish could be striking really on the nighttime drive. It has eight stinging tentacles which could measure ten meters in diameter when spread out.
• The class of Cubozoa – It inhabits in the water of tropical and subtropical seas. It is also known as sea wasps and box jellyfish. They possess an umbrella in form of a cube having four sides. Their sting is so powerful and may cause even death in just a few minutes if not treated with an antidote.
• The class Anthozoa – It includes madrepores, corals, sea anemones, and actinias. Generally, these species have beautiful colors. Some live in isolation such as beadle anemone (Actinia equine), some anemones such as Cerianthus membranaceus (color tube anemone), and others such as red gorgonians (Paramuricea sp.) and corals form colonies.

Health Benefits of Jellyfish

Jellyfish contains calcium-binding proteins which are helpful to maintain healthy cells and are considered an age-fighting solution and are also good for the human brain. It has collagen that maintains firm and young skin. Let’s learn more about the health benefits of Jellyfish:

1. Cut off weight – The presence of low calories with significant carbohydrates makes it an excellent choice for making a weight loss diet. In fact, it is a great source of protein which assists to maintain healthy muscle during the diet, and amino acids assist in the continuation of cell regeneration.
2. Build memory – Jellyfish is a type of seafood that is beneficial for memory. This sea creature has calcium binding protein in remarkable amounts. This protein is produced by the brain itself but as people age, its production is reduced progressively.
3. Prevent brain-related problems – As mentioned from the previous point, the same calcium-binding protein content found in jellyfish is also good to reduce the risk of several brain diseases which is aging-related but also some fatal conditions such as Alzheimer’s and dementia.
4. Promote cognition – Besides its benefit for the brain, calcium-binding protein is beneficial for counteracting age-associated cognitive decline because the nerve system in the brain should be well maintained. The consumption of jellyfish helps to optimize the regeneration of cells in the brain which also includes the nerve system.
5. Reverse aging – Jellyfish is known as an immortal creature being able to fix itself. Though the consumption of jellyfish does not make one immortal but slows down the aging process.
6. Impressive amounts of collagen – Mentioned previously that jellyfish keeps one look younger due to the presence of collagen in jellyfish. The human body also normally produces collagen through the metabolism process of Vitamin C. The consumption of jellyfish makes one reap all the benefits in it.
7. Skin appearance – Collagen is much beneficial for maintaining skin health. It assists in keeping the elasticity of skin even when getting older. Collagen helps to support the regeneration of skin cells for keeping it firm and young for a longer time.
8. Added to cosmetics  – Jellyfish is used as a vital cosmetic ingredient due to its content of collagen. This creature has the ability to transform old cells into younger cells.
9. Makes heart-healthy – Jellyfish has a low content of calories and carbohydrates and is loaded with amino acids and protein. Jellyfish are beneficial for the heart. Jellyfish is safe seafood for those having heart problems.
10. Lowers high blood pressure – Jellyfish are able to lower symptoms of high blood pressure. It helps to lower health risks associated with high blood pressure such as stroke and heart attack.
11. Normalize blood pressure – Jellyfish is able to maintain the level of blood pressure and prevents hardening of arteries for maintaining healthy blood vessel.
12. Antioxidant – Piraino wants to take this further and work out how to make use of all sorts of jellyfish. For instance, he says that if you break collagen into smaller pieces it acts as an antioxidant, a molecule that is deemed healthy because it helps soak up chemicals called radicals that can damage cells. And a few years ago, he isolated a compound from the Mediterranean fried egg jellyfish (Cotylorhiza tuberculate) that appears to have anticancer activity. He is now working to find out whether the compound is effective against a range of different cancers. The ultimate goal is to have it approved as a medicine. As part of a project called Pulmo, Piraino is trying to work out what other useful compounds there are in the Mediterranean sea lung jellyfish (Rhizostoma Pulmo). In late 2018, he published evidence showing that the contents of jellyfish ovaries can kill bacteria. As part of the larger GoJelly research consortium, which is exploring sustainable uses for jellies, he is also working out how best to cook jellyfish so as to best preserve the healthy molecules they contain when raw. At present, most of the jellyfish that is consumed is in China, where it is caught, then dehydrated with salt. People then soak it in water before eating it. Piraino has investigated what happens when it is instead boiled in water, looking to see what compounds the resulting material contains so we can be sure it’s safe to eat. So far, his work has shown that sea lung jellyfish performed better than the two others he has tested, in terms of retaining their healthy antioxidant compounds. So what do jellyfish taste like? Perhaps surprisingly, jellyfish end up being crunchy to chew once cooked. And it tends to take on the flavors it encounters during cooking, which means it can vary widely. Piraino says the one he found lying on the beach wasn’t the best he’s ever tasted. That was cooked for him in Milan by Gennaro Esposito, a well-known TV chef in Italy.
13. Excellent source of selenium – Jellyfish is an excellent source of selenium, an essential mineral that plays a major role in several important processes in your body. It has been shown to have antioxidant properties, protecting your cells from oxidative stress (13Trusted Source). As such, adequate selenium intake has been linked to a reduced risk of several illnesses, including heart disease, certain forms of cancer, and Alzheimer’s disease (14Trusted Source, 15Trusted Source, 16Trusted Source). Additionally, selenium is important for metabolism and thyroid function (17Trusted Source). While jellyfish is rich in this important mineral, more research is needed on the benefits of eating this marine animal species.
14. High in choline – Choline is an essential nutrient that many Americans don’t get enough of (18Trusted Source, 19Trusted Source). With 10% of the DV for choline found in 1 cup (58 grams) of dried jellyfish, it’s considered a good source (7Trusted Source) Choline has many important functions in the body, including DNA synthesis, nervous system support, the production of fat for cell membranes, and fat transport and metabolism (18Trusted Source, 19Trusted Source, 20Trusted Source). It has also been linked to improvements in brain functioning, including better memory and processing. It may even help reduce symptoms of anxiety. However, more research is needed (21Trusted Source, 22Trusted Source, 23Trusted Source). Despite the benefits of eating more choline-rich foods, research on the effects of consuming jellyfish specifically is needed.
15. Good source of collagen – Many of the proposed therapeutic benefits of jellyfish are thought to be due to its rich collagen content (8Trusted Source, 24Trusted Source). Collagen is a type of protein that plays an essential role in the structure of tissues, including tendons, skin, and bone. Consuming collagen has also been linked to various potential health benefits, including improved skin elasticity and reduced joint pain (25Trusted Source, 26Trusted Source). Specifically, collagen from jellyfish has been analyzed for its potential role in lowering blood pressure. One test-tube study on collagen from ribbon jellyfish found that its collagen peptides exhibited significant antioxidant and blood-pressure-lowering effects (27Trusted Source). Similarly, another 1-month study in rats with high blood pressure observed that the daily intake of jellyfish collagen significantly reduced blood pressure levels. While promising, these effects have not yet been studied in humans (28Trusted Source). Additional animal studies have noted that jellyfish collagen protected skin cells from sun damage, improved wound healing, and helped treat arthritis. Still, these effects have not been studied in humans (29Trusted Source, 30Trusted Source, 31Trusted Source).
    Jellyfish is low in calories yet high in protein, antioxidants, and several minerals, particularly choline and selenium. While animal studies suggest jellyfish collagen may have health benefits, including reduced blood pressure, human studies are lacking

How to Eat

• It is processed into dried products.
• Jellyfish is used in preparing sushi, salads, main courses, and noodles.
• In Asian countries such as Korea, China, Vietnam, Taiwan, and Japan, pickled and dehydrated jellyfish are regarded as a delicacy.
• Jellyfish salad is made by using cold marinated jellyfish which is thinly sliced.
• In Thailand, jellyfish is used for making crunchy style noodle.

Precautions                                                                                                 

• Jellyfish stings could be painful and even dangerous to humans. The stings occur accidentally not purposely.
• The symptoms of jellyfish stings include itching, stinging or intense pain, raised welts, and rash.
• Vomiting, nausea, lymph node swelling, diarrhea, abdominal pain, muscle spasms, and tingling/numbness are its progressive effects.
• People might experience coma, difficulty breathing, and even death as severe reactions.
• It should be consumed in dried form because jellyfish are decayed within few hours and is very toxic.

Other Facts        

• Jellyfish are termed as non-aggressive, free swimming, and gelatinous marine animals with tentacles.
• Tentacles are covered with nematocysts (sacs) which are loaded with venom (poison) and their sting might be painful to sometimes life-threatening.
• The family includes marine animals such as box jellyfish, jellyfish, hydroids, Portuguese man-of-war, fire coral, anemones, and hydroids.
• Jellyfish could be found throughout the world and deadly ones are found in Australian and Indo-Pacific waters.
• Usually, jellyfish are found near the water surface during diminished light floating in the water column.
• Over 200 types of jellyfish are documented.
• Often they could be translucent or transparent.
• The group of jellyfish is known as swarm, bloom, and smack.
• They do not have brains.

References

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